1. Field of the Invention
This invention relates to a high strength grouted pipe coupler by which pairs of spaced axially aligned steel reinforcement bars (i.e. rebars) are reliably spliced to one another for the purpose of connecting together and providing continuous support for contiguous precast or cast-in-place columns, walls, beams, and similar concrete structures to enable buildings, parking structures, bridges, subways, airports, and the like, to be better able to survive a seismic event.
2. Background Art
It is common in the construction industry, during the erection and retrofitting of buildings, parking structures, bridges, subways, airports, etc., to add a new contiguous concrete structure to an existing precast concrete structure. Care must be taken during construction to ensure that the contiguous structures are interconnected so that they will not shift relative to one another, particularly as a consequence of a seismic event. The foregoing has typically been accomplished by means of splicing together steel reinforcement bars (commonly known as rebars) that are embedded in and project from the existing and new structures so as to provide continuous reinforcement between the structures, whereby the structures will be capable of withstanding shear forces as well as tensile and compressive loads.
It has been known to use cement grout filled pipe couplers to splice together opposing rebar upstands that are embedded in the existing and new concrete structures. Such pipe couplers are usually made from steel by means of a casting process which increases the cost of construction, especially when large numbers of couplers are used in a project. In addition, the conventional pipe coupler requires a relatively long cylindrical pipe so as to prevent a separation of the rebars from their couplers in response to strong pulling forces.
In this same regard, the majority of stress experienced by conventional cement grout filled pipe couplers are concentrated along the interface of the reinforcement bar with the cement grout with which the cylindrical pipe of the coupler is filled. Consequently, the reinforcement bars can be undesirably loosened from or pulled out of their pipe couplers under compression and tension forces, such as those generated during an earthquake. To overcome this problem, the rebar has been provided with pronounced ribs along the length thereof to enhance the bond between the reinforcement bar and the cement core which fills the cylindrical pipe of the coupler. In other cases, a special, high strength cement grout has been used to preserve the integrity of the pipe coupler. In both of these solutions, the cost and complexity of manufacturing and/or installing known conventional grouted pipe couplers are increased which leads to an overall inefficient and possibly unreliable construction effort.
Accordingly, it would be desirable to have a relatively low cost, high strength and readily available cement grouted pipe coupler that will overcome the problems associated with conventional pipe couplers so as to be capable of reliably splicing together a pair of opposing embedded reinforcement bars and withstanding decoupling under tension and compression loads like those generated during an earthquake.
Reference may be made to the following application and patents for examples of conventional grouted pipe couplers:
European Application 92117276.3 published Jun. 23, 1993 PA1 U.S. Pat. No. 3,540,763 issued Nov. 17, 1970 PA1 U.S. Pat. No. 4,627,212 issued Dec. 9, 1986 PA1 U.S. Pat. No. 5,366,672 issued Nov. 22, 1994